EFFECTS OF NONLINEAR PHASE-SHIFTS ON THE PERFORMANCE OF A PHASE-CONJUGATE INTERFEROMETER

We present a theory of the effects of various sources of nonlinear pha se shifts or the performance of a phase-conjugate interferometer that uses degenerate four-wave mixing in the retroreflected pump-beam confi guration in determining the complex (magnitude and phase) third-order nonlinear susceptibility of novel nonlinear optical materials. Our ana lysis reveals that the performance of the interferometer is insensitiv e to the net nonlinear phase shift acquired by the pump wave in a doub le pass through the nonlinear material. However, the interferometer is susceptible to nonlinear phase shifts through the four-wave mixing pr ocess. As a consequence, under certain conditions a finite phase is me asured by the interferometer for the real third-order susceptibility o f a lossless nonlinear material. This measured phase depends on the in tensity imbalance between the forward and the backward pump beams as w ell as the intensity of the probe beam. The effects of the intensity i mbalance between the pump beams on the measured phase can be compensat ed for by a judicious choice of the intensity of the probe beam.